Mou Xuejie, Chai Huixia, Duan Cheng, Feng Yao, Wang Xiahui
Institute of Ecological Protection and Restoration Planning/Yellow River Ecology and Environment Protection Center, Chinese Academy of Environmental Planning, Beijing 100041, China.
Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
Plants (Basel). 2024 Oct 8;13(19):2814. doi: 10.3390/plants13192814.
Assessing vegetation changes in alpine arid and fragile ecosystems is imperative for informed ecological restoration initiatives and adaptive ecosystem management. Previous studies primarily employed the Normalized Difference Vegetation Index (NDVI) to reveal vegetation dynamics, ignoring the spatial heterogeneity alterations caused by bare soil. In this study, we used a comprehensive analysis of NDVI and its spatial heterogeneity to examine the vegetation changes across the Three-River Headwaters Region (TRHR) over the past two decades. A random forest model was used to elucidate the underlying causes of these changes. We found that between 2000 and 2022, 9.4% of the regions exhibited significant changes in both NDVI and its spatial heterogeneity. These regions were categorized into six distinct types of vegetation change: improving conditions (62.1%), regrowing conditions (11.0%), slight degradation (16.2%), medium degradation (8.4%), severe degradation (2.0%), and desertification (0.3%). In comparison with steppe regions, meadows showed a greater proportion of improved conditions and medium degradation, whereas steppes had more instances of regrowth and slight degradation. Climate variables are the dominant factors that caused vegetation changes, with contributions to NDVI and spatial heterogeneity reaching 68.9% and 73.2%, respectively. Temperature is the primary driver of vegetation dynamics across the different types of change, with a more pronounced impact in meadows. In severely degraded steppe and meadow regions, grazing intensity emerged as the predominant driver of NDVI change, with an importance value exceeding 0.50. Notably, as degradation progressed from slight to severe, the significance of this factor correspondingly increased. Our findings can provide effective information for guiding the implementation of ecological restoration projects and the sustainable management of alpine arid ecosystems.
评估高寒干旱脆弱生态系统中的植被变化对于开展明智的生态恢复举措和适应性生态系统管理至关重要。以往研究主要采用归一化植被指数（NDVI）来揭示植被动态，却忽略了裸土导致的空间异质性变化。在本研究中，我们综合分析了NDVI及其空间异质性，以考察过去二十年三江源地区（TRHR）的植被变化。我们使用随机森林模型来阐明这些变化的潜在原因。我们发现，在2000年至2022年期间，9.4%的区域在NDVI及其空间异质性方面均表现出显著变化。这些区域被分为六种不同类型的植被变化：状况改善（62.1%）、恢复生长（11.0%）、轻度退化（16.2%）、中度退化（8.4%）、重度退化（2.0%）和荒漠化（0.3%）。与草原地区相比，草甸状况改善和中度退化的比例更高，而草原恢复生长和轻度退化的情况更多。气候变量是导致植被变化的主导因素，对NDVI和空间异质性的贡献率分别达到68.9%和73.2%。温度是不同类型变化中植被动态的主要驱动因素，对草甸的影响更为显著。在重度退化的草原和草甸地区，放牧强度成为NDVI变化的主要驱动因素，重要性值超过0.50。值得注意的是，随着退化程度从轻度发展到重度，该因素的重要性相应增加。我们的研究结果可为指导生态恢复项目的实施和高寒干旱生态系统的可持续管理提供有效信息。
